Many things can happen before, during, and after a volcanic eruption. A volcanic eruption is an extraordinary thing. You never know what is going to turn out as in the end.
Before a volcanic eruption you may notice that the scenery slightly changes. The volcano is covered with lakes, streams, homes, old growth trees, along with many private homes and hotel resorts. Convection currents that move the plates, and cause movements make earthquakes and volcanoes. One of the many things that can happen before an explosion is the magma with in the volcano rises and collects in large chambers, the pressure decreases, and the magma expands. Every volcano has some sort of cap. The cap of a volcano is sort of a plug that holds everything in. While the magma expands in the center of the volcano the ground picks up its heat level, enlarges itself, and it also starts to slant. Volcanoes and earthquakes are activated when the convection currents move the plates in the seduction zone and cause the heat to re-melt the crust. Earthquakes and the magnitude may change months prior to the eruption.